Lilly estimated a quotient of 120 and found an actual quotient of 83. what should she do next? explain.

After she worked out the problem, she had a discrepancy (disagreement) of
about 45% between her estimate and the quotient. 

That's a lot !  There's almost definitely a major mistake somewhere, and
there really isn't any way to tell whether the mistake is in the estimate or
in the quotient. 

My answer to the question is that Lilly has to go all the way back to the
beginning, and do the whole thing again. Only this time, she has a harder
job to do:  She not only has to make another estimate and work out the
division problem again.  This time, she also has to find the mistake that
she made the first time ... and there may be more than one of them.

Cthe residual plot for model 1 has a non random pattern and is a good fit for the data